A “central venous catheter” (CVC), also known as a “central line,” “central venous line,” or “central venous access catheter,” is a catheter placed into a large vein. Catheters, such as the known 3 lumen catheter of FIG. 1, can be placed in veins in the neck (internal jugular vein), chest (subclavian vein or axillary vein), groin (femoral vein), or through veins in the arms (also known as a peripherally inserted central catheters (PICC) line). It is used to administer medication or fluids that are unable to be taken by mouth or would harm a smaller peripheral vein, obtain blood tests (specifically the “central venous oxygen saturation”), and to measure central venous pressure. FIGS. 2A and 2B illustrate catheters having been inserted into patients.
More than 50 million surgical procedures were performed in the United States. As part of some of those procedures, central venous catheters are inserted into patients. Before a catheter is placed into a patient, a guidewire must be inserted in the blood vessel to act as a guide for the catheter. The guidewire has become an integral part of a growing number of medical procedures with its use steadily increasing and expanding into more and more medical specialties, particularly as non-invasive procedures have been developed.
A guidewire is a thin, flexible, medical wire inserted into the body to guide a larger instrument, such as a catheter, central venous line, or feeding tube. The materials used to make guidewires have varied over the years but today they primarily consist of stainless steel and Nitinol (nickel titanium). Not all of a guidewire is placed into a patient as the guidewire must be retrievable after insertion of the catheter. As used herein, the phrase “the patient-side of the guidewire” will be used to refer to at least the end of the guidewire that is inserted into the patient.
The placement of a central venous catheter is frequently necessary for patients in the operating room or the intensive care unit. In fact, millions were placed last year in the United States alone. These are large IVs that are typically placed in the neck, shoulder, or groin. The blood vessel is penetrated with a hollow needle and a guidewire is then advanced through the needle into the vessel. In some embodiments, guidewire diameters range in size from 0.012″ to 0.063″, but smaller or larger guidewires can be used depending on the operation. In known configurations, a matching needle and catheter used with its corresponding guidewire has a hole with an inner diameter that is 10-30% larger than the diameter of the corresponding guidewire. The needle is removed, leaving the wire in place, and the catheter is advanced over exposed or doctor end of the guidewire until the first part of the wire extends outside the back of the catheter. (The term “doctor” as used herein is intended to mean both doctors and any medical professionals working under the supervision of a doctor (e.g., an intern, resident or surgical nurse).) Then, while holding the wire in place so that it does not move, the catheter is advanced into proper position within the vessel. Once the catheter is in place the wire is removed and discarded.
The most common complications of central venous catheters are infection and damage to surrounding structures. A less common but more serious complication is the accidental failure to remove the guidewire after placement and at times after the operation is complete—leaving the guidewire fully retained within the body. Despite the rare occurrence (approx. 1 per 3,000 placements), these retained guidewires cause significant potential harm to the patient including more surgeries, more lengthy hospital stays, additional medical problems, and potentially death. That 1:3,000 number correlates to over 2,000 occurrences annually in the US alone. Mortality rates with retained guidewires is as high as 1 in 5.
There are detailed procedures in place to assure that guidewires are never inadvertently left in patients. These include checklists, instrument counts, and careful training. Nonetheless, these events continue to happen due to human error. The most common cause is catheter advancement into the body over the wire before the guidewire is threaded the entire length of the catheter so that the lagging or doctor end of the wire can be gripped by the user and held in place during advancement. Consistent factors noted in many investigations include operator fatigue, distractions, emergency situations, and inexperience. These human factors cause safety steps to be forgotten or skipped in the interest of expediency or deviated from due a confluence of uncommon events. Almost all safety steps in place require the operator to perform various safety checklists even though human factors often reduce their reliability. Very little safety engineering has been done to modify equipment and reduce the potential for human error.
The market for guidewires is now global and growing. Market data shows this market to be about $1 billion globally each year and growing at a CAGR of 8.2%.
An exemplary set of steps for installing a known catheter is provided below. (The same or similar procedures are used for many other types of operations in which a guidewire is used to place a catheter.)                1. A needle is inserted into the blood vessel at a location on the body where the catheter is to be placed.        2. Guidewire is pushed through the needle into the blood vessel.        3. Guidewire continues to be pushed into the blood vessel to the appropriate depth so that the guidewire remains in the vessel once the needle is removed.        4. The needle is removed over the exposed or doctor end of the guidewire while leaving the guidewire in place.        5. A catheter is advanced over the exposed or doctor end of the guidewire and into position so that the leading tip of the catheter is completely in the blood vessel.        6. The guidewire is removed through the catheter and discarded, leaving the catheter in proper position.        7. The catheter is secured in place with sutures and/or adhesive dressing to maintain proper position.        
FIGS. 3A and 3B illustrate (using different shading techniques for clarity) a guidewire similar to a known guidewire where a portion of the guidewire has been shown segmented for illustration purposes only. In the left-hand portion of FIG. 3A, the portion of the catheter to be inserted into the patient (i.e., the patient side portion of the guidewire) has a “J” shape to it. This is common in some guidewires—though not mandatory. The J shape helps offers a blunt leading edge so that the wire does not puncture the lining of the blood vessel and/or unintentionally perforates the vessel. The J shape is configured to be very flexible (i.e., have a low coefficient of springiness so that it can be easily straightened or bent during introduction and then return to its previous shape).
FIG. 3C is an expanded view of the segmented portion of the guidewire of FIGS. 3A and 3B and illustrates the internal and external structure of a portion of the guidewire of FIGS. 3A and 3B. As shown in FIG. 3C, coils of the guidewire surround a straight inner wire core.